Hydraulic safety device for screw elevators



Feb. 3, 1953 J BRUBAKER 2,627,321

HYDRAULIC SAFETY DEVICE FOR SCREW ELEVATORS Filed Dec. 23, 1950 3 Sheets-Sheet 1 3|wentor Feb. 3, 1953 J. A. BRUBAKER 2,627,321

HYDRAULIC SAFETY DEVICE FOR SCREW ELEVATORS Filed Dec. 23, 1950 3 ts- 2 3uvcmor I Jo/m Aao /r firuba/Ter W WMNW,

Feb. 3, 1953 .1. A. BRUBAKER HYDRAULIC SAFETY DEVICE FOR SCREW ELEVATORS Filed Dec. 23, 1950 3 Sheets-Sheet 3 Ihwcmor A? Jo/mAoo/r Erato/Fer Ctlomcga-s Patented Feb. 3, 1953 HYDRAULIC SAFETY DEVICE FOR SGREW ELEVATORS John A. Brubaker, Toledo, Ohio, assignor to Haughton Elevator Company, lioledo, Ohio, :a

corporation of Ohio Application December 23, 1950, Serial No. 202,508

a Claims. 1

This invention relates to screw driven elevators and in particular to hydraulic safety devices for cushioning the descent of the elevator shouldthe lifting mechanism fail.

Screw-type elevators, in which the-oar is supported on a threaded column, are subject t one danger, namely that the car canfall freely should the threads in the driving nut Wear on? or strip so that the screw can slide through the nut without resistance. This stripping of the threads may be the result of wear such that the remaining thread is unable to support the load of the elevator. The stripping of the threads may also result from jamming the car against its upper limit of travel at which time a severe overload is placed. on the screw threads of the screw and the nut.

The principal object of this invention is to provide a hydraulic system for cushioning the descent of the elevator car in the event that the threads in the drive nut fail.

Another object of the'invention is to employ the screw and screw casing of the elevator as a piston and cylinder which when filled with oil cushions the descent of the elevator car.

A still further object of the invention is to pro vide an overflow tank to accommodate the fluid displaced from the casing when the elevator and its screw are in their lowermost positions.

More specific objectsand advantages are apparent from the following descriptionof a prei ierred embodiment of the invention.

According to theinvention a casing sunk into the ground below the elevator, toaccommodate the supporting screw column of theelevator, is made of uniform size and a disk that is a close fit in the casing is attached to the bottom end of the screw eolumnto restrict the upward ffow of fluid along the screw column during descent of the elevator. The 'fiuid [displaced from the casing during the descent of the elevator is collected in a surge tank and returned to the casing during upward travel of the. elevator screw. The invention further contemplates. making the disk at the bottom end of the screw in the .form of a valve arranged to readily permit downward flow or" fluid into the casing below 'the screw but to restrict upward flow. Thus the disk, .acting .as a valve, causes the hydraulic fluid in'the casing to support at least part of the elevator load during downward movement of the elevator car while not appreciably increasing the load on the screw during upward movement of the car. The disk on the screw and its fit within the casing are selected according to the hydraulic fluid within the casing so that the maximum speed of descent of the elevator even if the threads in the drive nut are stripped is within safe limits.

A preferrediorm of the invention is illustrated in the accompanying drawings.

ill

In the drawings:

Figure I is anelevation, partly insection, of the operating mechanism of ,a screw-type elevator embodying the invention.

Figures II and III are vertical sections of the screw-type elevator embodying the invention showing the elevator car in its upper and lower positions respectively.

Figure IV is an enlarged, isometric view of a disk arranged at the lowerend of the elevator support screw and arranged to act as a valve in regulating the speedof the elevator car.

These specific figures and the accompanying description are intended merely to illustrate the invention but not to impose limitations on its scope.

An elevator embodying the invention includes a car having a floor I thatis supported on a subframe 2 which in turn is carried on a cross beam 3. The cross beam 3 is supported onablock 5. serving as a connection for the pper end of a supporting screw, column 5. The screw column 5 extends downwardly through a gear box ,6, in which is-rotatably mounted a drive nuthaving a screw thread engaginga screw thread I on the column 5. The rotatabledrive nut within the gear box 5 is operatively connected through a sl1aft.8,.coupling.9 andarmature shaft It to a drive motor I I that is mounted on a stand 52 erected from a foundation 13 at thebottom of theelevator hatchway. HA brake assembly i4 is also. erected fromthe stand 12 to cooperate with a brake drum-mounted onthe coupling 9. The brake assembly .l i, notshown in detail,.is of a spring set typeand is released byasolenoid that is energized whenever themotor H is energized. Acover 15 supported on rods I5 is provided to shield the motor and brake assembly from any debris falling in the elevator hatchw-ay.

A generally cylindrical casing or pipe H extends downwardly from the gear box 5 to accommodate the lower end'of the. screw column 5. The casing H is substantially as long as the screw column 5. The casing I1 is filled with hydraulic fluid which, when displaced by. downward movement of the screw 5,.flows up in the casing ll, out through a side pipe Iii and is collected in a surge, tank l9 mountedadjacent and at generally the same elevation as thegear box 6. Air displaced from thesurse tank I 9 escapes througha vent 20.

Referring now to Figures .11 and III, which show the elevator in its upper and lower].posithe car is lowered and the screw column 5 enters more deeply into the casing H the hydraulic fluid displaced by the descending screw 5 flows upwardly past the sides of the screw and through the pipe [8 into the surge tank [9. When the elevator and the screw reach their lowermost positions the surge tank I9 is nearly filled and also hydraulic fluid has risen into the gear box '6 to the same level as the level in the surge tank Hi. This maximum level for the hydraulic fluid is below the input shaft 8 of the gear box 6 so that the opening for the shaft 3 need not be sealed against a static head of fluid.

As may be seen in Figures I, II and III a valve disk assembly 22 is mounted on the lower end of the elevator support screw column 5. This assembly is shown in detail in Figure IV. The assembly 22 comprises a disk valve 23 that is a close fit within the casing I1 and that has a large central aperture 22 which preferably is slightly larger than half the root diameter of the threads I of the screw column 5. The disk 23, on its lower side, has a plurality of ribs 25 which when the elevator is at rest or movin upwardly engage a washer 25 mounted on a bolt 21 threaded into the bottom end of the screw 5. When the disk valve 23 is supported on the washer 26 a gap is left between the flat bottom end of the screw column 5 and the upper surface of the disk valve 23 so that hydraulic fluid may easily flow from the upper side of the disk valve 23 to the bottom through the gap, the central aperture 22 and out between the ribs 25 supporting the disk valve 23 from the washer 26.

little additional load during upward movement of the elevator car.

During downward movement of the elevator car the screw support column 5 displaces hydraulic fluid which must flow from the space beneath the valve assembly 22, past the valve disk 23 and up alongside the descending screw column 5. At nearly full speed the resistance to fluid flow through the central aperture 24 and through the gap between the flat bottom end of the screw column 5 and the disk valve 23 is sumcient to lift the disk valve upwardly against the end of the column 5 thereby interrupting fluid flow through this path. This forces the fluid to flow through the annular gap between the periphery of the disk valve 23 and the interior surface of the casing ll. The fluid pressure thus developed beneath the disk valve 23 is sufiicient to sustain the weight of the Z elevator car and load when it is moving downwardly at a safe speed but faster than normal speed. Thus regardless of whether the drive nut within the housing 6 is operating or not the downward velocity cannot exceed a'safe maximum speed.

column 5.

The disc valve 23 and washer 21' are protected from overload at the upper end of travel of the elevator by a heavy cylindrical pin 3| that, extending transversely through the column 5 and held in place by a cross pin 32, engages a This fluid path ofiers little restriction to e flow so that the hydraulic mechanism offers 4 steel collar at the bottom of the drive nut in the gear housing 6 to stall the drive before the disk valve 23 strikes any obstruction in its upward movement.

The hydraulic device just described and illustrated in the accompanying drawings provides a simple, easily constructed yet fully reliable safety device for protecting a screw-type elevator against failure of the support and driving mechanism.

Various modifications in detail of the valve and pipe arrangement may be made without departing from the spirit and scope of the invention.

Having described the invention, I claim:

1. In an elevator having a car guided for vertical movement, in combination, a threaded column that supports the car, a rotatable nut in a driving mechanism for supporting the column, a casing extending downwardly from the driving mechanism to receive the threaded column, said casing being liquid tight, a member on the lower end of the column that fits the interior of the casin throughout its range of travel, a hydraulic fluid in the casing, and means connected to the upper end of the casing to receive the fluid displaced from the casing by the threaded column.

2. In an elevator havin a car guided for vertical movement, in combination, a threaded column that supports the car and that engages a rotatable nut in driving mechanism, a liquid tight casing extending downwardly from the mechanism to receive the threaded column, a valve member on the lower end of the column, and hydraulic fluid in the casing, said valve being conditioned to ofier greater resistance to upward flow of fluid than to downward flow thereby resisting downward movement of the elevator car.

3. In an elevator having a car guided for vertical movement, in combination, a threaded column that supports the car and that engages a rotatable nut in a driving mechanism, a liquid tight casing extending downwardly from the mechanism to receive the threaded column, hydraulic fluid in the casing, means for receiving fluid displaced by the threaded column, and a member loosely mounted on the end of the column, said member having a shape to match the casing and an aperture of less extent than the bottom of the column, said member serving as a valve to permit downward flow of fluid and restrict upward flow.

4. In an elevator having a car guided for vertical movement, in combination, a threaded column that supports the car and that engages a rotatable nut in a driving mechanism, a casing extending downwardly from the mechanism to receive the column, hydraulic fluid in the casing, a vented receptacle connected to the casing to receive fluid displaced by the column, a reduced diameter extension depending from the column, an apertured plate loosely mounted on the extension, and means for supporting said plate from said extension without obstructing fluid flow through the aperture as the fluid flows downwardly in the casing.

JOHN A. BRUBAKER.

Name Date Anderson et a1 Jan. 16, 1940 Number 

